Water-tube boiler



July 10, 1928.

B. BROIDO WATER TUBE BOILER Filed Oct. 20, 1924 5 Sheets-Sheet EEA/Jfl/W/N, EEO/0. INVENTOR.

A TTORNE Y July 10, 1928. 1,676,631

B. BROIDO WATER TUBE BOILER Filed 001;. 20, 1924 3 Sheets-Sheet 2 EE/VJ/IMI/V. BRO/D0 4 IN V EN TOR A TTORNE V July 10, 1928.

B. BROIDO WATER TUBE BOILER Filed Oct. 20, 1924 5 Sheets-Sheet 3 .BE/VJAMl/V. .B/PO/DO. INVENTOR BY V M A TTORNEV Patented July 10, 1928.

UNI-TED STATES 1,676,631 PATENT OFFICE.

BENJAMIN BROIDO, OE NEW YORK, N. Y., ASSIGNOR TO THE SUPERHEATER COMPANY,

' OF NEW YORK, N. Y.

, WATER-TUBE BOILER.

Application filed October 20, 1924. Serial No. 744,668.

My invention relates to water tube boilers, and particularly to the type in which the evaporating surface is composed of two or 'more superimposed spaced banks of horizontally inclined tubes placed over the combustion chamber of the boiler, the tubes being arranged in rows and connected at their ends to upflow and downflow headers, with the space between the banks being utilized as the location for a steam superheater.

Heretofore, in boilers of this general type, the headers ofthe lower bank or banks have usually been connected intothe boiler circulation by means of nipples which connect them to the corresponding headers of the bank above, and it is through these nippled connections thatthe lower bank receives its water supply and discharges the steam evaporated. This construction makes it necessary for the headers of the upper bank to handle the circulation requirements, not only for the tubes of the bank of which they form a part, but for the lower bank as Well. So also in the case of boilers using box headers, the upper portions of the headersmust handle the supply to and discharge from the entire tube surface of the boiler.

The tubes of the lower bank, being exposed to the direct radiant heat of the incandescent combustion gases and to high temperature gases giving up heat by conrection, absorb heat with great rapidity and produce the major portion of the steam evaporated in the boiler. This rapidity of steam generation in the lower tubes is' satisfactorily takencare of by the nippledconstruction referred to when the boiler is operated at low or normal ratings, but at the high ratings necessary to meet peak loads the limited capacity of the upper headers leads to operating deficiencies which result in damage to or failure of tubes in both the upper and lower banks of the boiler. At

' high ratings, failure of tubes in the lower bank, due to overheating, is occasioned by either or both of two causes; e. g., inability of the downflow headers of the upperbank and the connecting nipples to supply water with sufficient rapidity to the lower tubes to replace that evaporated; and inability of the upflow headers and nipples to discharge to the drum, as rapidly as it is formed, the steam generated in the lower tubes. The result is that the lower tubes become partially or totally dry because of lack of an adequate water supply onbecause of -be--- coming steam bound through lack of an adequate steam outlet. Furthermore, steam discharged from the lower tubes into the headers is discharged to the bottom of what is virtually a water column the full height of the boiler, and must force its way to the steam drum through-this mass of water. Not only is the free discharge of the steam interfered with, but the steam bubbles in passing up through the water, act in the I manner of an air lift pump, and carry over into the steam drum undesirably large quantities of water.

The limited capacity of the upflow headers also exposes tubes in the upper bank to injury through'overheating, as the extreme velocity of the steam passing .upward through'these headers from the lower bank to the drum produces an ejector action on the tubes of the upper bank, which, coupled with the normal speed of flow through these tubes, is suflicient to drain them of their water content at a rate beyond that at which the downflow headers can supply them.

.The result is tubes totally or partially dry,

and liable to overheating.

The modern practice of operating boilers at very high ratings, resulting in the operating difliculties with the generating tubes which have just been described, has also led to extreme combustion chamber temperatures, particularly in cases where pulverized coal or oil have been used as fuels. These extreme temperatures have caused rapid deterioration of the refractory combustion chamber walls, and in order to minimize this loss, and with certain fuels to improve combustion conditions, steps have been taken in some recent installations to protect the refractory walls with screens composed of a number of closely spaced water tubes, which by the absorption of radiant heat from the gases, serve to lower their temperature and protect the combustlon chamber walls.

These screens are usually in the form of grids of vertical tubes connecting top and bottom headers, which are connected into the boiler circulation, and in cases where such screens are used for sidewall protection they may be extended, if so desired, above the top of the combustion chamber proper to the level of the upper bank of generating tubes. This practice of extending the sidewall screens above the interbank space affects the availability of the inter-bank space as a superheater location, as will appear more fully hereinafter.

In the form of Water screen previously referred to, it is necessary in order to make it effective, to have the individual tubes very closely spaced, if not actually contacting. Otherwise, a considerable area of the furnace side-walls is exposed to direct radiant heat and because of lack of adequate protection, deteriorates rapidly. As previously noted, however, the usual and most satisfactory form for water screens of this type is atube and header construction in which the screen is in the form of a grid composed of a number of parallel tubes joined at their ends by inlet andoutlet headers. As may readily be seen, this construction imposes very definite limitations upon the tube spacing, inasmuch as suflicient space must be left in the headers, between-the holes receiving the tubes, to provide the necessary ligament strength to withstand the boiler pressure. In order to provide the necessary spacing between the screen tubes, required by the headers, and at the same time furnish adequate wall protection, it has been proposed to form water screens of double rows of staggered tubes, or by tubes having metal fins welded thereto, the fins overlapping to form an unbroken metallic wall. .These expedients while affording the necessary wall protection, introduce undesirable complications in the screen structure, and to obviate these difficulties I have provided a form of water screen which combines complete wall ,protection with extreme simplicity, and which I will'describe in detail later.

The tubes forming the water screens oper-' ate under conditions substantially the same asthose to which the lower bank of boiler tubes are subjected. That is to say, they are exposed to extremely high temperatures and by radiation absorb heat with great rapidity, producing, together with the radiant heat tubes of the lower boiler bank, by far the greater amount of steam generated. 'Heretofore is has generally been proposed to supply waterto the screens and to take care of the discharge therefrom, by connecting them to the header sections of the boiler, these connections often being effected by omitting one or more of the boiler tubes and inserting the screenconnections in their stead. This construction has, however, led to the same operating difliculties with the screen tubes thathave been described in connection with the main boiler banks.

These deficiencies in this type of boiler have beenrecognized, and it has heretofore been proposed to insure an adequate Water supply to all of the generating tubes of the boiler by providing either separate upflow or downflow connections to the lowermost row of tubes, these connections 'usually taking the form of auxiliary conduits supplementing the ordinary connections through nipples to the upper bank. This construction, however, does not make adequate provision for the circulation requirements of screens, if they are used, and furthermore, it does not permit of the most advantageous location of the superheater, which in modern power plants has become so universally adopted that it must be considered a necessary part of every boiler installation.

In boilers of the type described the most desirable superheater location is in the space between the banks of generating tubes, as in this location advantage may be taken'of thehigh gas temperature tosecure high degrees of superheat with comparatively short lengths of superheating units, and consequent small pressure drop losses through the superheater. At the same time, the superheater is protected from excessive temperatures by the tubes of the lower bank which form a thermal' screen protecting the superheater from the radiant heat of incandescent gases in the combustion chamber.

To inake the most effective use of this locagitudinally of the generating tubes, and 1on gitudinally removable from the space between the banks, is most desirable, as this arrangement permits anefiicient thermal location of the units and insures ready removability, the space necessarily left at the ends of the boiler for the removal and replacement of generating tubes providing ample room for the removal of the superheater units. A further and most important advantage derived from the use of a longitudinally placed superheater is the flexibility of design which the arrangement permits. Boilers of the transverse drum type'are usually constructed of tubes and headers of certain standard lengths and the desired capacity for any individual boiler is obtained, as far as possible, by the use of the proper number of tube and header units across the boiler rather lecting the proper number of superheater units of a given standard size, to correspond to the width of boiler employed. This method of varying the capacity of the superheater, involving no change in the length of the superheater units, afi'ects in no way the pressure drop through the superheater, the superheat temperatures obtained and I other factors, all of which would be affected if the superheater were transversely placed and which in the latter case would mean the substantial redesigning of the superheater for every width of boiler employed.

Her'etofore, however, the longitudinal superheater arrangement just described has been rendered impractical, if not impossible, by the rows of nipples connecting the upfiow and downflow headers at eachend of the boiler. The superheater headers cannot be placed inside the nipples without exposing them and the joints to too high a temperature and also rendering the entire superheater inaccessible, while if the headers are placed outside the nipples, there is not sufficient space between the latter for the insertion of the required number of superheater units. Because of these limitations,

it has heretofore been customary to place.

superheaters between tube banks with the superheater units disposed transversely of the generating tubes and removable through the boiler side walls. This disposition of the superheater makes necessary a much more expensive side wall construction, and

where a battery of boilers is employed, necessitates an uneconomically .wide space being left between boilers to allow for removal of the superheater units from the settings. In order to reduce the space between boilers, short units have been used extending into the boilers from each side of the setting. but this construction involves an expensive duplication of superheater headers and piping. and in cases where two boilers are placed in a double setting. with the superheater units extending into the setting from each of the side walls thereof, .provision must be made for the removal of the long superheater units employed. This necessitates wide aisles between the boiler settings, involving loss of valuable boiler room floor space, longer steam lines, and other disadvantages so important as to make the most economical superheater location. in such cases, the space above the upper tube bank, where the superheater may be longitudinally placed and removed through side wall doors in the upper setting. though the latter location is not so desirable from the standpoint of efficiency as the inter-bank position, and involves placing the superheater header joints in a high temperature zone.

A's previously noted, it is desirable in somecases to extend the sidewall screens to a .screen tubes sary, if the desirable inter-bank location is to be used for the superheater, to make prov1s'1on for 1ts longitudinal removal.

It is my object, therefore, to eliminate the deficiencies in existing types above enumer-' ated by providing a boiler in which the evaporating surface isdivided into two virtually independent units in's uch a manner that the circulation requirements of all of the evaporating surfaces of the boiler are adequately taken care of at all times, and with the connections so arranged that the most efiicient superheater location may .be effectively utilized.

Division of the boiler into units is based upon the different thermal conditions to which different portions of the evaporating surface are subjected. In one unit are grouped all of the evaporating tubes which are exposed to the direct radiant heat of the incandenscent gases, while in the other unit are grouped the evaporating tubes which receive heat by convection only, from the gases after they leave the combustion chamdirectly over the combustion chamber, and I in cases where they are employed the protecting the combustion chamber walls, while in the latter unit, hereinafter referred to as the convected heat unit. are grouped the evaporating tubes comprising the bank or banks above the space forming the superheater location, and not exposed to radiant heat. I

The radiant'heat unit, producing large volumes of steam with great rapidity. is constructed so that a free discharge is permitted through independent connections to the steam space of the boiler, unimpeded by the restrictions in the convected heat unit and not affecting the latter bysthe production of excessive velocities therein. Independent supply connections from the boiler drum to the radiant heat unit may also be provided'in cases where itis desirable. The use of independent connections from the radiant heat. unit to the steam space also enables me to eliminate the nipples bridging the inter-bank space at one or both ends of the boiler, and to provide a construction whereby a superheater may be inserted longitudinally between the tube banks without interference or restriction from any boiler elements. This latter advantage I consider equally as important asthe pro vision of a free circulation to and from the radiant heat unitfi p The above and further objects and ad- III vantages will appear more fully from a consideration of. the following detailed descrip-' tion of two specific embodiments of my invention, taken in conjunction with the ac companying drawings, in which:

Fig. 1 is a vertical section of a boiler constructed according to my invention, the

1 section being taken along line 11 of Fig.

lit)

2; Fig. 2 is an elevation looking from the left of Fig. 1, portions of the boiler setting being broken away to expose the boiler structure; and Fig. 3 is a View. similar to Fig. 1, showing a slightly different form.

In Fig. 1, 1: indicates generally the furnace andpombustion chamber having a refractory Hill wall 2 and refractory side walls 3 andyt, 'which-are protected by the .water screen tubes 5, to be described in detail later. The furnace, for purposes of illustration only, is shown as adapted to be fired by pulverized fuel, though itis to be understood that in so far as my invention is concerned, solid. liquid or gaseous fuel may be employed with equal facility.

The steam generating tubes of the boiler are mounted directly above the combustion chamber and are arranged in two spaced,

.' banks, the upper bank being composed of 'a number of rows of horizontally inclined tubes 7 whilethe lower bank is composed of similar tubes 8. Preferably the lower bank comprises, in elevation, only a small number of rows and in the embodiments shown but two rows of tubes are employed. The tubes 7 are connected at their lower ends to sinuous vertical downtake headers 9 and at their upper ends to corresponding uptake headers 10. Above the headers 9 there is mounted a transverse steam and water drum 11, which is connected to each of the headers 9 by nipples 12. The headers 9 are also connected by means of nipples with a horizontal header 13, which serves as a settling chamber, and from which sediment and other impurities may be blown off from time to time in the usual manner through theconnection 14.

Thev up-take headers 10 extend above the level of the generating tubes 7 and the extended portions of the headers are connected with the transverse drum 11 by horizontal circulators 15. Preferably each header is connected to the drum by two circulators,

although the number of circulators for each upper tube banks.

bafiie 27 is supported by. the lowermost row nections 20. The upper horizontal headers 17, which receive the steam and water discharge from the tubes. 8, are nlppled at their ends into cast or forged fittings 21 which also extend through the boiler walls. Outside risers 22 connect each of the fittings 21 with header boxes 23, which in turn are connected to the drum 11 by short horizontal circulators 24, the latter entering the drum in the same manner as the circulators 15. As will be seen from Fig. 2, the header boxes 23 are located beyond the ends of the rows of-circulators 15, and connect only with drum 11, through the eirculators 24.

The portions of the boiler just described are supported from beams mounted upon the usual steel frame work, which forms no part of the present invention, and which need not be described in detail. As shown, the housin for the boiler comprises brick or other refractory side walls 25, and metallic front and rear walls 26, formed of removable units, which provide ready access to the interior of the boiler.

The closely spaced headers 9, 1O, 16 and 17 form substantially gas tight walls and serve to protect the metallic portion of the housing 26 from the combustion gases.

In the forms of boiler illustrated, the combustion gases rise vertically without restriction other than that imposed by the tubes, through the lower tube bank and the space intervening between the lower and A horizontally inclined of tubes 7 and extends from the header 9 to a point substantially midway of the tubes 7. A vertically inclined baffle 28 extends from the upper end of battle 27, transversely of the bank of tubes 7, and the transverse baffle 29, together with bafiie 28, serves to divide the upper bank of tubes 7 into three transverse gas passes of gradually diminishing cross sectional area, through which the combustion gases progressively pass to the outlet 30. In this general type of boiler, as previously noted, the most desirable superheater location is between the two banks of enerating tubes, and by the specific form of my invention I provide a boiler in which a superheater may be readily installed at this point, with the superheater headers located transversely of the boiler and outside the headers, the superheater units being parallel with the generating tubes and located in the most desirable position in the combustion gas path. As shown in Fig. 1, the superheater of the conventional tubular return bend type, which need not be described in detail, is mounted above the lower ends of the lower tubes 8, the tubular units 31 of the superremoved. Preferably this space .may

heater being suspended by hangers 32 from the upper tubes 7. The ends of the units 31 are extended through the open space'between headers9 and 16, and connect with the superheater inlet and outlet headers 33 and. 34 respectively. Headers 33 and 34 are mounted parallelto headers 16 and are so positioned as to be readily accessible through the removable cover plate 35 in the metallic front wall 26. The space between the tubes 7 and the tubes 8 and around the superheater units 31, where they extend out to the superheater headers, is closed with any suitable formof refractory material which is readily e closed by means of a' built-upwall of refractory fire brick, the ready removal of which allows easy access to and removal of the superheater units for the "purposes of cleaning, inspection, repair or replacement. The space between headers 10 and 17 is closed by means of a similar refractory wall, forming a gas-tight seal as at 36.

The superheater inlet header 33 is connected in the usual manner by means of the steam pipe 37 with the steam space of the drum 11, the superheated steam being delivered from the superheater outlet header 34 at the point 3 8.

In Fig. 1 I have shown water screens protecting only the sidewalls of the combustion chamber proper. Along the side of each combustion chamber sidewall, parallel to and in substantially the same horizontal plane asthe lowermost row of tubes 8, are pro-i vided the headers 39, into which are rolled or otherwise suitably secured the upper ends of a series of sidewall tubes 5, which form the water screen. At their lower ends, the headers 39 are blank, and at their upper ends they are nippled into the fittings 21, which carry the upper transverse headers 17. risers 22, connecting fittings 21 with drum 11, thus serve to carry the discharge of both the generating tubes 8 and screen tubes 5, forming the radiant heat unit, to the steam space of the boiler through a free and unrestricted path. At the bottom of the sidewalls, there are provided headers 40, s'milar to headers 39, into which the lower ends of the'tubes 5 are secured. At their upper ends headers 40 are blank, and at their lower ends they are connected into the boiler circulation by conduits 41, which form extensions of the downcomers 19 below the connections 18. Preferably, headers 39 and40 are horizontally inclined, as shown in Fig. 1, to facilitate circulation, but they may be placed horizontally or inclined at different angles if desired.

In order to provide the necessary spacing where the tubes 5 enter headers 39 and 40, and at the same time secure the necessary close spacing between the tubes themselves, I employ a special form of tube, in which The .the use of structure having large metal surfaces not in immediate contact with water.

It is to be particularly noted that according to my invention the evaporating surface which produces by far the greater amount of steam, that is, the lower generating tubes 8 and the side wall tubes 5, form a circulation circuit virtually independent of the remainder of the boiler,.and' by virtue of the large unrestricted passages connecting the evaporating surfaces wlth the steam and water drum, an ample supply of water to this sectionof the boiler is assured at all times, a free and unimpeded steam delivery to the drum is provided, and the carrying over to the stream drum of slugs of water from the uptake headers is eliminated.

It is also to be noted that the connection of the lower bank tubes and sidewall tubes into the outside risers 22 and downcomers 19, which are placed at the sides of the setting (as is clearly-shown in Fig. 2) and the elimination of nipples between the headers leaves free access between the tube banks at either end of the boiler for the insertion of a superheater, which may, in the construction shown in Fig. 1, be as readily installed from the rear end of the boiler as from the front end thereof.

A further feature of advantage resulting from the use of the particular form of risers I emplo to carry the discharge from the lower tu e tank, lies in the fact that the side wall tubes may be carried to any desired height and the same circulation scheme retained without resort to any material change in the boiler layout, resulting in a very desirable flexibility of design with respect to the side wall screens.

In Fig. 3 I have shown a boiler similar in general to that shown in'-. Fig. 1, but illus trating the use of screens extending above the inter-bank space. "In order to use this type ofscreen it is only necessary to place the upper screen headers, indicated at 39, in the side wall at the desired height and connect the upper ends thereof into the conveniently placed risers 22 by means of fittings 21', similar to the fittings 21, connecting the upper headers of the lower tube bank into the risers.

I havefurther shown the superheater in Fig. 3 extending into the interbank space from the upper end thereof, and with the lower ends of the tubes 8; extending into short vertical headers 42, which are connected in the conventional manner to the headers 9 by the nipples 43. In this case the downcomers 19 serve to supply only the lower screen headers 40'. Where the super heater is extended into the interbank space from the upper end thereof, as in Fig. 3, the refractory structure sealingthe space. between the headers of the tube banks and around the superheater units, as shown in Fig. 1, may be modified, and in the structure illustrated in Fig. 3 I have shown a seal for this space composed of a pair of removable metal plates 44, engaging the headers of the upper and lower banks and removable therefrom, thespace between said plates being filled with any suitable insulating material 45. In all other respects the construction shown in Fig. 3 is similar to that shown in Fig. 1, and need not be described in detail.

It will be obvious that the position of the superheater could be reversed in the structure shown in Fig. 1, audit is also obvious that the form of screen shown in Fig- 3 is equally applicable to the structure 'shown in Flg. 1. These and similar changes and modifications are, however, intended to be within the scope of my invention, as defined in the appended claims.

What I claim is:

1. In a water tube boiler, a steam and water drum, spaced upper and lower banks of horizontally inclined upfiow generating tubes, said banks of tubes terminating at one end in correspondingly spaced headermeans, independent connections from each of said header means to said drum, said connections being constructed and arranged to leave the space between said header means free and unobstructed, and superheater units extending between said spaced header means into the space between said banks.

2. In a water tube boiler, a steam and water drum, spaced upper and lower banks of horizontally inclined. upfiow generating tubes, said banks of tubes terminating at one end in correspondingly spaced header means, independent connections from each of said .header means to said drum, said connections being constructed and arranged to leave the space between said header means free and unobstructed, superheater headers adjacent said superheater headers into the space between said banks.

3. In a Water. tube boiler, a steam and water drum, spaced upper and lower banks of horizontally inclined upfiow generating tubes, said upper bank terminating at one end in vertical header means, said lower bank terminating at the corresponding end in horizontal header means, independent connections from each of said header means to said drum, said connections being constructed and arranged to leave the space between said header means free and unobstructed, and superheater units extendingbetween said spaced header means into the space betweensaid banks. I

4. In a water tube boiler, a steam. and water drum, spaced upper and lower banks of horizontally inclined .upflow generating tubes, said upper bank terminating in vertical upfiow and downflow header means, said lower bank terminating in horizontal inlet and outlet header means, independent connections from each of said header means to said drum, said connections being constructed and arranged to leave'the space between said header means free and unobstructed, and superheater units extendingbetween said spaced header means into the space between said banks.

5. In a water tube boiler, .a steam and water drum, water evaporating surfaces including two spaced upper and lower units,

said upper unit comprisinga bank of horizon-v structed, and superheater units extending between said spaced header means into the space between said banks.

6. Ina water tube boiler, a steam and "water drum, water evaporatin surfaces including two spaced upper an lower units, said upper unit comprising abank of horizontally inclined upflow generating tubes,

said lower unit comprising a bank of horizontally inclined upfiow generating tubes,

said banks of tubes terminating at one end in correspondingly spaced header means, independent connections from each of said header means to said drum, said connections being constructed and arranged to leave the space between said header means free and unobstructed, superheate'r'headers adjacent the space between said header means, and tubular superheater units extending from said superheater headers into the space between said banks.

BENJAMIN BROIDO.

no I 

